GameLib.D3.API.Quaternion = function (x, y, z, w, axis, angle) {

    if (GameLib.D3.Utils.UndefinedOrNull(x)) {
        x = 0;
    }
    this.x = x;

    if (GameLib.D3.Utils.UndefinedOrNull(y)) {
        y = 0;
    }
    this.y = y;

    if (GameLib.D3.Utils.UndefinedOrNull(z)) {
        z = 0;
    }
    this.z = z;

    if (GameLib.D3.Utils.UndefinedOrNull(w)) {
        w = 1;
    }
    this.w = w;

    if (GameLib.D3.Utils.UndefinedOrNull(axis)) {
        axis = new GameLib.D3.API.Vector3();
    }
    this.axis = axis;

    if (GameLib.D3.Utils.UndefinedOrNull(angle)) {
        angle = 0;
    }
    this.angle = angle;
};

GameLib.D3.API.Quaternion.prototype.translate = function (v) {
    this.x += v.x;
    this.y += v.y;
    this.z += v.z;
    return this;
};

GameLib.D3.API.Quaternion.prototype.copy = function () {
    return new GameLib.D3.API.Quaternion(
        this.x,
        this.y,
        this.z,
        this.w
    );
};

/**
 * Note, this normalize function leaves 'w' component untouched
 */
GameLib.D3.API.Quaternion.prototype.normalize = function () {

    var EPSILON = 0.000001;

    var v2 = this.x * this.x + this.y * this.y + this.z * this.z;

    if (v2 < EPSILON) {
        return this; //do nothing for zero vector
    }

    var invLength = 1 / Math.sqrt(v2);

    this.x *= invLength;
    this.y *= invLength;
    this.z *= invLength;
};

GameLib.D3.API.Quaternion.prototype.multiply = function (q) {

    var x, y, z, w;
    var a = q;
    var b = this;

    if (q instanceof GameLib.D3.API.Matrix4) {

        x = a.rows[0].x * b.x + a.rows[0].y * b.y + a.rows[0].z * b.z + a.rows[0].w * b.w;
        y = a.rows[1].x * b.x + a.rows[1].y * b.y + a.rows[1].z * b.z + a.rows[1].w * b.w;
        z = a.rows[2].x * b.x + a.rows[2].y * b.y + a.rows[2].z * b.z + a.rows[2].w * b.w;
        w = a.rows[3].x * b.x + a.rows[3].y * b.y + a.rows[3].z * b.z + a.rows[3].w * b.w;

        this.x = x;
        this.y = y;
        this.z = z;
        this.w = w;

        return this;

    } else if (q instanceof GameLib.D3.API.Quaternion) {

        x = ((a.x * b.x) - (a.y * b.y) - (a.z * b.z) - (a.w * a.w));
        y = ((a.x * b.y) + (a.y * b.x) - (a.z * b.w) + (a.w * a.z));
        z = ((a.x * b.z) + (a.y * b.w) + (a.z * b.x) - (a.w * a.y));
        w = ((a.x * b.w) - (a.y * b.z) + (a.z * b.y) + (a.w * a.x));

        this.x = x;
        this.y = y;
        this.z = z;
        this.w = w;

        return this;

    } else {
        console.log("This functionality not implemented - please do this");
        throw new Error("This functionality not implemented - please do this");
    }
};

GameLib.D3.API.Quaternion.prototype.setFromAngle = function (angle) {

    this.instance.setFromAxisAngle(this.axis.instance, angle);

    this.x = this.instance.x;
    this.y = this.instance.y;
    this.z = this.instance.z;
    this.w = this.instance.w;

    return this;
};

GameLib.D3.API.Quaternion.prototype.subtract = function (v) {

    if (v instanceof GameLib.D3.API.Vector3) {
        this.x -= v.x;
        this.y -= v.y;
        this.z -= v.z;
    }

    if (v instanceof GameLib.D3.API.Quaternion) {
        this.x -= v.x;
        this.y -= v.y;
        this.z -= v.z;
        this.w -= v.w;
    }

    return this;
};

GameLib.D3.API.Quaternion.prototype.magnitude = function () {
    return Math.sqrt(
        (this.x * this.x) +
        (this.y * this.y) +
        (this.z * this.z) +
        (this.w * this.w)
    );
};

GameLib.D3.API.Quaternion.prototype.normalize = function () {

    var magnitude = this.magnitude();

    if (magnitude < 0.000001) {
        return this; //do nothing for zero vector
    }

    this.x *= magnitude;
    this.y *= magnitude;
    this.z *= magnitude;
    this.w *= magnitude;

    return this;
};

/**
 *
 * @param matrix4 GameLib.D3.Matrix4
 */
GameLib.D3.API.Quaternion.prototype.setFromRotationMatrix = function(matrix4) {

    this.instance.setFromRotationMatrix(matrix4.instance);

    this.x = this.instance.x;
    this.y = this.instance.y;
    this.z = this.instance.z;
    this.w = this.instance.w;
};

/**
 *
 * @param quaternion GameLib.D3.Quaternion
 * @param t
 * @returns {GameLib.D3.Quaternion}
 */
GameLib.D3.API.Quaternion.prototype.slerp = function (quaternion, t) {

    this.updateInstance();

    this.instance.slerp(quaternion.instance, t);

    this.x = this.instance.x;
    this.y = this.instance.y;
    this.z = this.instance.z;
    this.w = this.instance.w;

    return this;
};